High volume elcetronic gas regulator

ABSTRACT

A gas regulator ( 14 ) is provided for regulating the pressure of a gas flowing from a source ( 12 ) of the gas under pressure to a device ( 24 ) for using the gas. The regulator ( 14 ) includes a housing ( 26 ) and a pressure reducing valve ( 36 ) in the housing for controlling the flow of gas from an inlet ( 28 ) under pressure to an outlet ( 32 ) at a regulated pressure. The pressure reducing valve is controlled by a pressure responsive member ( 40, 44 ) which is displaced by operating feed and bleed valves ( 50 ) coupled to a control chamber ( 46 ) of the pressure responsive member. The feed and bleed valves are operated by a high speed solenoid actuator ( 68 ). The bleed valve is vented to the outlet of the housing from the control chamber which is maintained at a higher pressure. The high speed solenoid actuator ( 68 ) is operated by a controller ( 18 ) for controllably varying the output pressure as desired.

FIELD OF THE INVENTION

[0001] The present invention relates to gas pressure regulators and moreparticularly to regulators for regulating pressure in large volume,highly dynamic flows of gas.

BACKGROUND

[0002] One of the technical challenges facing the natural gas vehicle(NGV) industry, and other pressurised gas using devices, is the need foran accurate, reliable pressure regulator to supply gas to the system.Currently, mechanical (analogue) regulators are being used that haveinherent errors due to dynamic droop, hysteresis, and supply-pressureeffects. These are single-stage or two-stage designs that use either adiaphragm or a piston coupled to a valve to control pressure. Durabilityhas been a problem with a number of regulators. Some regulators havebeen prone to failures of the valve-seat, diaphragm, and o-rings. Othershave been reported to jam or stick in the open position, or resonate(squawking, honking).

[0003] To address these concerns an electronic regulator has beendeveloped that is controlled by a proportional-integral-derivative (PID)controller. This regulator is described in U.S. Pat. No. 6,003,543,filed Jun. 11, 1997, the disclosure of which is incorporated herein byreference. The regulator includes a high-speed solenoid valve, apressure sensor, and an electronic control unit. This regulator cansignificantly improve the accuracy of the injector supply pressure byreducing droop (steady-state error), hysteresis, and the error due tochanges in storage tank pressure. However, this system at present canonly meet the fuel flow requirements of smaller engines.

[0004] U.S. Pat. No. 3,455,323 to Haupt, provides a gas regulator usingelectronic pressure control. The regulator includes a housing having aninlet, an outlet and a regulator valve for controlling flow through thehousing from the inlet to the outlet. A pressure responsive membersupported in a control chamber within the housing controls displacementof the regulator valve. The control of pressure in the control chamberhowever requires multiple valves each having a solenoid to control thebleeding and feeding of the control pressure in the control chambertherethrough. The arrangement of valves and solenoids is complex toassemble upon manufacture and requires awkward manipulation in use.Furthermore, the valves are arranged to be vented to the atmosphere whenbleeding gas from the control chamber which is undesirable when the gasto be regulated involves fuels and the like which are typically notfriendly to the environment.

[0005] British Patent Application 2 121 563 provides a pressureregulating apparatus for gaseous and liquid flow media. The apparatusincludes a housing having an inlet, an outlet and a regulator valvecontrolled by a pressure responsive member mounted in a control chambersimilarly to the above noted U.S. patent to Haupt. Control of thepressure in the control chamber however requires a complex arrangementof ports and valves for selectively feeding or bleeding the controlchamber on both sides of the pressure responsive member. Furthermore,bleeding of the control chamber on both sides of the pressure responsivemember requires venting externally of the housing. This is undesirableas noted above when regulating pressure of fuels and the like whichshould not be vented to the atmosphere.

[0006] The present invention is concerned with certain improvements togas regulators for large volume, highly dynamic flows of gas whichaddress some of the deficiencies of the above noted prior art.

SUMMARY

[0007] According to one aspect of the present invention there isprovided a gas pressure regulator for regulating the pressure of a gasflowing from a source of the gas under pressure to a device for usingthe gas, the regulator comprising:

[0008] a regulator housing having a gas inlet for receiving the gas anda gas outlet for the delivery of the gas from the housing;

[0009] a pressure reducing valve in the housing for controlling the flowof gas from the inlet to the outlet;

[0010] a pressure reducing valve controller comprising:

[0011] a control chamber;

[0012] a feed valve having an inlet for receiving gas from said sourceof gas under pressure and a control pressure outlet coupled to thecontrol chamber, the feed valve having an open state in which the valveis fully open and a closed state in which the valve is fully closed;

[0013] a bleed valve having an inlet coupled to the control chamber andan outlet coupled to the gas outlet of the regulator housing, the bleedvalve having open state in which the valve is fully open and a closedstate in which the valve is fully closed;

[0014] a high speed solenoid valve actuator for operating the feed andbleed valves;

[0015] a pressure responsive member in the control chamber and coupledto the pressure reducing valve for movement therewith, the pressureresponsive member being movable in response to variations in a controlpressure in the control chamber;

[0016] a pressure monitor for monitoring an actual gas pressure at thegas outlet of the regulator housing;

[0017] a controller coupled to the pressure monitor and to the solenoidvalve actuator for controlling operation of the feed and bleed valvesbetween their respective closed and open states to produce a desired gaspressure at the gas outlet of the regulator housing.

[0018] The regulator of the present invention provides an effectivemeans of regulating pressure of large volume, highly dynamic flows ofgas using a pressure reducing valve which is simple in design and use.The arrangement of the bleed valve is particularly useful for ensuringthat gaseous fuels being regulated are not vented to the atmosphere, butrather are vented to the outlet of the regulator where the fuel can besubsequently consumed with the pressure regulated gaseous fuel exitingthe regulator.

[0019] This regulator is of the piston or diaphragm type, with thepressure responsive member, e.g. piston or diaphragm, moving in responseto a pressure difference across the member, and controlling the pressurereducing valve. In this case, the control pressure is supplied by thegas being regulated, under the control of feed and bleed valves. Thisallows the rapid regulation of the supply pressure with a limited energyinput. The back pressure is the outlet pressure.

[0020] To adjust the regulator in response to a reduced gas or fueldemand, the control chamber pressure must be reduced using the bleedvalve. Because the control gas may be gaseous fuel, it is not acceptableto bleed this gas into the atmosphere, so that the gas used for controlis bled from the control chamber into the gas outlet of the regulatorhousing to be used as fuel.

[0021] The use of a high speed solenoid actuator for the feed and bleedvalves allows the same kind of dynamic control of the control pressurethat can be achieved with the pressure control system disclosed in priorU.S. Pat. No. 6,003,543, referred to above, but for much larger flowrates.

[0022] The solenoid valve actuator may be a single solenoid coil openingand closing the feed and bleed valves in opposition. Pulse widthmodulation and/or frequency modulation may be used to vary the ratio ofopen and closed times and thus the pressure in the control chamber.Alternaively, two coils may be used for the two valves. This allowsindependent control of the valves to compensate for inertial effects,for example pressure spikes or time lags in flow changes, in response torapid changes in flow demand.

[0023] The desired gas pressure at the gas outlet is preferably a setpoint pressure. The controller thus preferably comprises a mechanism forcontrollably varying the set point pressure.

[0024] The controller preferably includes a signal generating mechanismfor delivering a pulsed electrical signal for operating the feed andbleed valves and a signal varying mechanism for controllably varying thepulse width of the electrical signal.

[0025] The high speed solenoid valve actuator preferably includes apressure reducing valve closing mechanism for closing the pressurereducing valve in response to deactivation of the high speed solenoidvalve actuator. This arrangement provides a positive shut-off forensuring no gaseous fuel is released from the regulator in the event ofa failure or loss of power to the solenoid valve actuator.

[0026] In a preferred embodiment, the feed and bleed valves are coupledfor movement together between a bleed position in which the bleed valveis in the open state and the feed valve is in the closed state and afeed position in which the feed valve is in the open state and the bleedvalve is in the closed state. The high speed solenoid valve actuatorwould thus preferably comprise a single solenoid coupled to the feed andbleed valves with the feed and bleed valves being positioned in thebleed position upon deactivation of the single solenoid.

[0027] The feed and bleed valves are preferably both coupled tocommunicate with the control chamber on a first side of the pressureresponsive member. A port may then be provided coupling the controlchamber on a second side of the pressure responsive member to the gasoutlet of the regulator housing such that back pressure on the secondside of the pressure responsive member is substantially equal to theactual gas pressure at the gas outlet. A biasing mechanism mayadditionally be provided on the second side of the pressure responsivemember acting in a direction corresponding to closing the pressurereducing valve.

[0028] There may be provided a shut-off valve coupled to the gas inletof the regulator housing. When closed, the shut-off valve ensures thatthe gaseous fuel is not leaked through the regulator housing when thedevice using the pressure regulated gas is not intended to be used.

[0029] The shut-off valve may include a solenoid operating mechanism fordisplacing the valve between respective open and closed positions. Thesolenoid operating mechanism is preferably arranged to be oriented inthe closed position when de-energised to ensure that it operates as itis intended, for closing the flow of gaseous fuel in the event of apower loss or failure. The shut-off valve is preferably arranged to beclosed in response to a shut-off condition sensed by the pressuremonitor which may include a signal from the device using the gas that itis being shut-off or a signal from the controller indicating a failure.

[0030] According to a second aspect of the present invention there isprovided in combination:

[0031] a supply of pressurised gas;

[0032] a gas using device for using the gas; and

[0033] a gas pressure regulator coupled to the gas using device and thesupply of pressurised gas for controlling the pressure of gas deliveredfrom the supply to the gas using device, said pressure regulatorcomprising:

[0034] a regulator housing having a gas inlet for receiving the gas anda gas outlet for the delivery of the gas from the housing;

[0035] a pressure reducing valve in the housing for controlling the flowof gas from the inlet to the outlet;

[0036] a pressure reducing valve controller comprising:

[0037] a control chamber;

[0038] a feed valve having an inlet for receiving gas from said sourceof gas under pressure and a control pressure outlet coupled to thecontrol chamber, the feed valve having an open state in which the valveis fully open and a closed state in which the valve is fully closed;

[0039] a bleed valve having an inlet coupled to the control chamber andan outlet coupled to the gas outlet of the regulator housing, the bleedvalve having open state in which the valve is fully open and a closedstate in which the valve is fully closed;

[0040] a high speed solenoid valve actuator for operating the feed andbleed valves;

[0041] a pressure responsive member in the control chamber and coupledto the pressure reducing valve for movement therewith, the pressureresponsive member being movable in response to variations in a controlpressure in the control chamber;

[0042] a pressure monitor for monitoring an actual gas pressure at thegas outlet of the regulator housing;

[0043] a controller coupled to the pressure monitor and to the solenoidvalve actuator for controlling operation of the feed and bleed valvesbetween their respective closed and open states to produce a desired gaspressure at the gas outlet of the regulator housing.

[0044] In a gas using system, when the supply of pressurised gas ismounted remotely from the gas using device, coupled by a gas line, thegas pressure regulator is preferably mounted adjacent the supply ofpressurised gas. The pressure monitor is then preferably coupled to thegas line adjacent the gas using device so that the gas line coupling thesupply to the gas using device is at the regulated pressure instead ofthe much greater supply pressure. This is particularly useful in agaseous fuelled vehicle wherein the fuel lines coupling the pressurisedgaseous fuel tank to the engine can be maintained at the regulatedpressure instead of the supply pressure of the fuel tank while stillbeing able to accommodate the varying pressure requirements of fuel tobe delivered to the engine.

[0045] The regulator according to the present invention may beincorporated into various gaseous fuelled devices or gas consumingsystems, including the following:

[0046] 1) as a stand alone regulator coupled within the gas line at anylocation between a supply and a gas using device;

[0047] 2) as a regulator integrated with a tank valve and a tanksolenoid to produce one component;

[0048] 3) as a regulator for vehicles with gaseous fuelled combustionengines including natural gas fuelled vehicles (NGVs) and the like; and

[0049] 4) as a regulator for vehicles with fuel cell powered engines forregulating fuel supplied to the fuel cell of the vehicle.

[0050] According to a further aspect according to the present inventionthere is provided a method of regulating pressure of a gas flowing froma source under pressure to a device for using the gas, the methodcomprising:

[0051] providing a regulator housing having a gas inlet, a gas outletand a pressure reducing valve for controlling the flow of gas from theinlet to the outlet;

[0052] connecting the gas inlet in communication with the source underpressure;

[0053] connecting the gas outlet in communication the device for usingthe gas;

[0054] providing a pressure reducing valve controller having a controlchamber, a feed valve and a bleed valve, each of the feed and bleedvalves having an open state in which the valve is fully open and aclosed state in which the valve is fully closed;

[0055] connecting the feed valve to the source under pressure at aninlet of the feed valve and to the control chamber at an outlet of thefeed valve;

[0056] connecting the bleed valve to the control chamber at an inlet ofthe bleed valve and to the gas outlet of the regulator housing at anoutlet of the bleed valve;

[0057] providing a pressure responsive member in the control chamber;

[0058] coupling the pressure responsive member to the pressure reducingvalve for movement therewith in response to variations in controlpressure in the control chamber;

[0059] monitoring an actual gas pressure at the gas outlet of theregulator housing; and

[0060] controlling, in response to the actual gas pressure monitored,operation of the feed and bleed valves between their respective closedand open states to produce a desired gas pressure at the gas outlet ofthe regulator housing.

[0061] The operation of controlling the bleed valve preferably includesventing the control chamber to the gas outlet of the regulator housing.

[0062] The control pressure in the control chamber is preferablymaintained substantially greater than the actual gas pressure at the gasoutlet of the regulator housing.

[0063] While the invention has been developed with a view to itsapplication in gaseous fuelled vehicles, electronic regulators can alsobe used as stand-alone regulators in other applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In the accompanying drawings, which illustrate exemplaryembodiments of the present invention and graphs representing certaintest data:

[0065]FIG. 1 is a schematic illustration of one embodiment of theregulator;

[0066]FIG. 2 is a schematic illustration of a second embodiment of theregulator;

[0067]FIG. 3 is a schematic of a further embodiment of the regulator;

[0068]FIG. 4 is a cross-sectional view of the pressure reducing valve ofthe embodiment of FIG. 3;

[0069]FIG. 5 is a graph showing the variations in outlet pressure andflow rate with time in a single stage mechanical regulator;

[0070]FIG. 6 is a graph like FIG. 5 for an electronic regulatoraccording to the present invention;

[0071]FIG. 7 is a graph showing the variation of outlet pressure withflow rate in a single stage mechanical regulator;

[0072]FIG. 8 is a graph like FIG. 7 for an electronic regulatoraccording to the present invention;

[0073]FIG. 9 is a graph showing the variation of outlet pressure withchanges in inlet pressure over time with a single stage mechanicalregulator;

[0074]FIG. 10 is a graph like FIG. 9 for an electronic regulatoraccording to the present invention;

[0075]FIG. 11 is a comparative plot of the results of power tests on avehicle;

[0076]FIG. 12 is a comparative plot of the results from part of astandard test procedure; and

[0077]FIG. 13 is a graph showing the variation of outlet pressure of theelectronic regulator with a ramp change in set point pressure.

DETAILED DESCRIPTION

[0078] Referring to the accompanying drawings, and particularly to FIG.1 initially, there is illustrated a gaseous fuel system 10 that includesa fuel supply 12 of pressurized gaseous fuel. Gas from the supply isdelivered to a regulator 14. The regulator has an operating component 16controlled by a processor 18 which receives the feedback from a pressuresensor 20. The regulator delivers gaseous fuel at a regulated pressureto the fuel metering device 22 of a gas using device 24, for example aninternal combustion engine.

[0079] The regulator 14 includes a regulator housing 26. This has a gasinlet 28 connected to the fuel supply 12 and discharging into an inletchamber 30 in the housing. The housing also has a gas outlet 32 from anoutlet chamber 34 and connected to the fuel metering device 22. Betweenthe inlet chamber 30 and the outlet chamber 34 is a pressure reducingvalve 36. The pressure reducing valve 36 includes a pressure reducingvalve seat 38 and a pressure reducing valve head 40 that moves towardsand away from the seat to vary the size of the opening between the two,thus providing a variable restriction in the flow of gas from the inletchamber to the outlet chamber. A spring 42 biases the pressure reducingvalve head 40 towards engagement with the seat 38.

[0080] A piston 44 is coupled to the pressure reducing valve head 40 andreciprocates in a cylindrical chamber 45 in the housing, separating thatchamber into an outlet regulated chamber 47 on one side and a closedcontrol chamber 46 on the other. A control port 48 couples the controlchamber 46 to an outlet 64 of a three-way valve 50.

[0081] The three way valve 50 includes both a feed valve having a feedvalve seat 54 and a bleed valve having a bleed valve seat 56. These twovalve seats cooperate with a valve body 58 having a feed valve head 60and a bleed valve head 62 engageable with the seats 54 and 56respectively. The valve body 58 thus ensures that the feed and bleedvalves are operable together between a respective feed position and arespective bleed position of the three way valve 50 in which pressurisedgas is either fed or bled from the control chamber 46 through thecontrol port 48.

[0082] The feed valve, including the feed valve seat 54 and the feedvalve head 60, connects the control port 48 to the pressurised supply 12through a feed valve inlet 52 for supplying pressurised gas to thecontrol chamber when the feed valve is opened. Alternatively, the bleedvalve, including the bleed valve seat 56 and the bleed valve head 62,connects the control port 48 to a bleed port 66 for bleeding pressurisedgas from the control chamber when the bleed valve is opened. The bleedport 66 is connected to the gas outlet 32 of the regulator housing at ableed inlet 67 as indicated in FIG. 1 for bleeding the pressurised gasfrom the control chamber to the gas outlet of the regulator housing.

[0083] The three way valve 50 is controlled by a solenoid operatingmechanism 68 with an operating coil 69. In operation, the valve operatesbetween the respective feed and bleed positions. In the feed position,the feed valve is fully open, with the head 60 disengaged from the seat54 while the bleed valve is fully closed, with the bleed valve head 62engaged with the valve seat 56. In the bleed position, the feed valve isfully closed by the feed valve head 60 engaging the seat 54, while thebleed valve is fully opened by the bleed valve head 62 being disengagedwith the seat 56. The solenoid operating mechanism 68 is operated underthe control of the processor 18 using a square wave signal that is pulsewidth modulated and/or frequency modulated to provide the desired outputpressure as detected by the pressure sensor 20.

[0084] The controller 18 has a set point input 72 for representing thedesired output pressure from the regulator. This can be fixed orvariable. This provides a more precise control of engine operation tomeet not only fuel demand but emission standards and other parameters.The processor uses a proportional, integral and derivative (PID) controlalgorithm. The solenoid operating mechanism provides a very accuratecontrol of the pressure in the control chamber which is balanced by thesum of the pressure in the inlet chamber 30 and the force of spring 42.The spring is selected to provide an adequate force to close thepressure reducing valve 36 when the outlet pressure is above the setpoint, or when the system is inoperative.

[0085] An alternative embodiment of the regulator is illustrated in FIG.2, where the feed and bleed valves are operated by separate high-speedsolenoid operating mechanisms. The feed valve 76 includes a solenoidoperating mechanism 78, while the bleed valve 80 includes its ownsolenoid operating mechanism 82. This provides for independent controlof the feed and bleed functions. This can be used to improve the bleedrate where the bleed valve 80 has a larger flow area. This has theadditional benefit of allowing the dome to be fed, bled or heldconstant, reducing pressure fluctuation. In terms of hardware, the lifeof the solenoid operating mechanism is improved because of reducedoperation.

[0086] Both the first and second embodiments include a high pressurelock-off solenoid 86. The lock-off solenoid 86 is a valve, controllablebetween a fully open position and a fully closed position by a solenoidoperating coil arranged in such a manner that the lock-off solenoid isoriented in the fully closed position when the operating coil isde-energised.

[0087] The lock-off solenoid 86 is controlled by the controller 18 forshutting off the gaseous fuel supplied to the regulator in response toshut-off condition as determined by the controller. The shut-offcondition comprises a shut-off signal from the controller in the eventthat the controller detects a failure or receives a signal from the gasusing device that the gas using device is turned off. The high pressurelock-off solenoid 86 thus ensures that gaseous fuel is not leakedthrough the regulator housing when the regulator and gas using devicecoupled thereto are intended to be shut-off.

[0088] Referring now to FIGS. 3 and 4 a further embodiment of theregulator is generally indicated by reference numeral 100. The regulator100 is intended for use with a gaseous fuel system 110 similar to thepreviously described systems of FIGS. 1 and 2. The fuel system 110includes a supply of pressurised gas 112 in a high pressure vessel,typically in the form of a tank, mounting an electronic regulator havingan operating component 116 located in, on, or near the high pressurevessel. The supply 112 is mounted remotely from a gas using device 118arranged to use the gas. The gas using device 118 may comprise acombustion engine, a fuel cell arrangement or any other suitablepressurised gas using device. Gas is delivered from the supply 112through a pressure reducing valve within the operating component 116 ofthe regulator to a fuel line 120 at a regulated pressure. The fuel line120 delivers the gas at the lowered regulated pressure to the fuelmetering system 122 of the gas using device 118. A pressure sensor 124is mounted along the fuel line 120 adjacent the fuel metering system 122of the gas using device such that the regulator is arranged to regulatethe pressure of the flow entering the metering system. The sensor 20provides feedback to a processor 126 which subsequently controls theoperating component 116 of the regulator.

[0089] The operating component 116 of the regulator is illustrated infurther detail in FIG. 4. A housing 128 of the regulator includes a gasinlet 130 (perpendicular to the plane shown) connected directly to thefuel supply 112 for discharging into an inlet chamber 132 in thehousing. A gas outlet 134 is also provided in the housing fordischarging gas from an outlet chamber 136 in the housing to the fuelline 120 connected to the gas using device.

[0090] A pressure reducing valve 138 is mounted between the inlet andoutlet chambers to provide a variable flow restriction to the gasflowing from the inlet chamber to the outlet chamber. The pressurereducing valve 138 includes a pressure reducing valve seat 140 and apressure reducing valve head 142 movable towards and away from the seatbetween open and closed positions to vary the size of the opening andthus vary the restriction of flow between the inlet and the outlet.

[0091] An optional heating jacket 143 is mounted within the housing 128to surround the pressure reducing valve 138. The heating jacket 143heats the area surrounding the valve seat 140 and the inlet of thepressure reducing valve 138 to compensate for the heat which is absorbedby the gaseous fuel as it expands through the pressure reducing valve138. This is particularly useful when regulating gaseous fuels likenatural gas which absorbs a considerable amount of heat from itssurroundings upon expansion.

[0092] The pressure reducing valve head 142 is mounted on a piston 144for sliding movement therewith within a bore 146 in the housing. Thebore 146 defines a portion of the outlet chamber 136 surrounding thepressure reducing valve head 142. A counter bore 148 of greater diameterthan the bore 136 defines the control chamber 150 of the regulator. Thepiston 144 is sealed with respect to the bore 146 at 152 so as toprovide a seal between the control chamber 150 and the outlet chamber136.

[0093] The piston 144 includes a portion of increased diameter whichdefines a pressure responsive member 154 which divides the controlchamber into a first side 156 and a second side 158. The pressureresponsive member 154 is sealed about its periphery 160 with respect tothe counter bore 148 to provide a pressure seal between the first andsecond sides of the pressure responsive member while remaining slidablewith respect to the housing. Pressure is controlled in the controlchamber on the first side of the pressure responsive member forcontrolling the position of the piston and the pressure reducing valve138 coupled thereto.

[0094] A port 162 extending through the piston 144 connects the outletchamber 136 to the second side 158 of the pressure responsive member154. The port 162 ensures that the back pressure on the second side ofthe pressure responsive member is substantially equal and balanced withthe actual gas pressure at the outlet of the housing.

[0095] A spring 164 is mounted on the second side of the pressureresponsive member 154 to act in a direction corresponding to urging thepressure reducing valve head 142 to engage the valve seat 140 in aclosed position of the pressure reducing valve 138. The spring 164 thusacts to displace the pressure responsive member 154 in the samedirection as the back pressure on the second side 158 so as to besubstantially balanced with the control pressure within the controlchamber 150 on the first side 156 of the pressure responsive member.

[0096] The spring is selected so as to permit a large pressuredifferential between the control pressure on the first side of thepressure responsive member and the outlet pressure on the second side ofthe pressure responsive member. The large pressure differential allowsfor rapid response time when venting the control pressure on the firstside of the control chamber to the outlet chamber of the housing.

[0097] The control pressure in the control chamber 150 is controlled bya control port 166 which is coupled to the chamber on the first side 156of the pressure responsive member. The control port 166 connects thecontrol chamber 150 to a feed valve 168 and a bleed valve 170.

[0098] The feed valve 168 includes a feed valve head 172 which ismovable with respect to a feed valve seat 174 between an open state inwhich the valve is fully opened and a closed state in which the valve isfully closed. Similarly the bleed valve 170 includes a bleed valve head176 which is movable with respect to a bleed valve seat 178 between anopen state in which the valve is fully opened and a closed state inwhich the valve is fully closed. The feed valve 168 and the bleed valve170 are linked for operation together between a feed position in whichthe feed valve is in the open state and the bleed valve is in the closedstate and an alternative bleed position in which the bleed valve is inthe open state and the feed valve is in the closed state.

[0099] Similarly to the previous embodiments, the feed valve is coupledat an inlet to the inlet chamber 132 and at an outlet to the controlport 166 of the control chamber, while the bleed valve is connected atan inlet to the control port 166 of the control chamber and at an outletto the gas outlet 134 of the housing. In the feed position, pressurisedgas is thus supplied through the control port 166 from the inlet chamber132 to the control chamber 150 on the second side of the pressureresponsive member 154. The increase in pressure acts to open thepressure reducing valve.

[0100] Alternatively in the bleed position pressurised gas from theinlet chamber 132 is prevented from entering the control port 166 andthe control pressure in the control chamber 150 is thus vented throughthe control port 166 and subsequently through a bleed port 180 couplingthe bleed valve 170 to the outlet chamber 136 of the housing.. This actsto close the pressure reducing valve. A large pressure differentialbetween the control pressure in the control chamber and the actualpressure at the outlet of the housing 128 ensures rapid response whenventing.

[0101] The feed valve 168 and the bleed valve 170 are coupled togetherby an actuator rod 182 which connects the valves to a high speedsolenoid operating mechanism 184. The solenoid operating mechanism 184is operated by the processor 126 as described in the previousembodiments using a square wave signal that is pulse width modulatedand/or frequency modulated to provide the desired control pressure inthe control chamber 150 to consequently provide the desired outputpressure as detected by the pressure sensor 124 (as shown in FIG. 3).

[0102] A set point 186 is input into the processor 126 to represent thedesired output pressure from the regulator. The set point may be variedelectronically to meet the demands of the gas using device 118 through arange of performance conditions. The processor 126 uses a proportionalintegral and derivative control algorithm to control operation of thesolenoid operating mechanism 184 in accordance with the set point 186.

[0103] When installing the gaseous fuel system 110 in an existingvehicle equipped for operation with conventional gasoline fuel, thepressure supplied to the metering system may be modified by modifyingthe set point as a means for controlling the amount of fuel injectedinto the engine, in addition to pulse width modulation, to extend thedynamic range of the injectors of the metering system.

[0104] The particular arrangement of the regulator in FIG. 4 also actsas a shut off valve when the solenoid operating mechanism 184 isdeactivated. Upon deactivation of the solenoid operating mechanism, thefeed and bleed valves are displaced into the bleed position thus ventingthe controlled pressure on the first side of the control chamber 150 tothe gas outlet 134 of the housing 128 such that the control pressure onthe first side of the pressure responsive member and the back pressureon the second side of the pressure responsive member are both balancedwith the actual gas pressure at the gas outlet 134. The spring 164 thuscloses the pressure reducing valve 138. The regulator may further beused as an integral shut off valve mounted directly on a tank ofpressurized gas by selectively deactivating the solenoid operatingmechanism 184 when it is desired to shut off supply from the tank.

[0105] A high pressure lock-off solenoid 190 is provided, similarly tothe previous embodiments, coupled between the supply 112 and the inletof the regulator housing 128. The high pressure lock-off solenoid 190ensures that gaseous fuel is not leaked through the regulator housing128 when the regulator and gas using device are intended to be shut-offas described in the previous embodiments.

[0106] The regulator housing 128 may further include a pressure reliefvalve to relieve excess pressure in the event that one of the operatingelements or valves of the regulator fails.

[0107] The electronic regulator described herein provides a means ofcontrolling pressures of gaseous fuels being delivered to a gas usingdevice such as a fuel cell or an internal combustion engine. Theregulator is capable of providing improved pressure control for dynamicgas flow typically ranging from 0 to 20 g/s. The system has beendesigned so that fuel is not bled or purged to the atmosphere in normaloperation. Further, the regulator has been designed such that a springcloses the pressure reducing valve when the system is de-energized. Aswell, additional safety is provided by a high pressure lock-off solenoidthat shuts off the gas supply to the regulator system when theelectronic controller de-energizes the lock-off solenoid.

[0108] The primary function of the controller, which includes amicroprocessor containing embedded software, is to control the outletpressure to a pre-programmed set point or set function. Themicroprocessor controls on-board electronic driver circuitry which inturn controls the 12 volt high speed solenoid operating mechanism whichoperates the feed and bleed valves. The pulse width or energized time ofthe solenoid operating mechanism is controlled by the microprocessorusing PID control and feedback from the downstream pressure transducer.The high speed solenoid of the solenoid operating mechanism may befrequency modulated or pulsewidth modulated to vary the ratio ofenergized time to de-energized time which in turn has a directrelationship on the feed to bleed ratio, thus allowing the pressurewithin the control volume to be manipulated resulting in a change inforce on the piston/valve causing movement against the counter spring toreestablish the static force balance on the piston/valve unit. Thismovement of the piston/valve assembly is manipulated to maintain thedesired output pressure despite variations in fuel demand and supplypressure.

[0109] Method of Analysis

[0110] Performance Parameters

[0111] Tests were conducted to compare the performance of the electronicregulator with a single-stage mechanical regulator for a natural gasvehicle (NGV) fuel system. The tests were also conducted using atwo-stage mechanical regulator, but those results are not included herefor the sake of simplicity. The results for the two stage mechanicalregulator were sufficiently similar to those for the single stageregulator that they are not considered necessary for a completeunderstanding of the present invention. Each regulator was set up on atest bench and tests were conducted to evaluate the followingparameters:

[0112] Dynamic droop: This is defined as the decrease in regulatoroutlet pressure as a function of increasing flow rate. It is dueprimarily to the change in spring force as the valve moves away from theseat, but it is also due in part to pressure drop after the seat. Forthe purposes of this comparison droop was defined at a maximum air flowrate of 20 g/s.

[0113] Inlet pressure effect: Supply pressures in NGVs decrease from3600 to 150 psig as the vehicle consumes the stored natural gas. Theinlet or supply pressure effect is the variation of outlet pressure as afunction of supply pressure. This is typically due to inlet pressureforces on the pressure reducing valve that change the force balance onthe valve assembly. It is quoted in units of psig/1000 psig of supplypressure.

[0114] Hysteresis: Hysteresis is caused by friction and can be difficultto eliminate. As the flow rate increases the outlet pressure decreasesor droops along a certain trajectory or path; however, the pressurefollows a different path when the flow decreases. The difference betweenthe two outlet pressure paths is called the hysteresis. It appears thatthe friction of the diaphragm pintle assembly (or o-ring on apiston-type regulator) is different depending on whether the valve isopening or closing.

[0115] Cracking droop: Cracking droop is the difference between thestatic pressure and the flowing pressure.

[0116] Cyclic variations: This is an indication of the fluctuations or(noise) in outlet pressure. For the electronic regulator it can becaused by the opening and closing of the pilot valve. For mechanicalregulators it can be cause by cycling of the fluid dynamic systemconsisting of the spring, valve, and diaphragm.

[0117] Maximum error: This is defined as the overall error of theregulator over an air flow rate of up to 20 g/s and a tank pressuredecreasing from 3000 psig to zero. It includes droop, hysteresis, andinlet pressure effect and is calculated from the following formula:

Maximum Error=Droop+Hysteresis/2+Inlet Pressure Effect×3000/1000  (1)

[0118]  One-half the hysteresis is assumed because it is assumed thatthe regulator starts out at the average set-point pressure (as definedbelow).

[0119] Average set-point pressure: For the purpose of estimating thepercent maximum error, average set-point pressure was defined as theaverage of the outlet pressure before and after the test.

[0120] Percent maximum total error:

Percent Maximum Error=Maximum Error/(Average Set-PointPressure+14.7)  (2)

[0121] It is usually possible to compensate for regulator droop in thecalibration tables in the power train control module. However, it isdifficult to compensate for hysteresis which results from changes due tofriction.

[0122] After bench testing, the electronic regulator was installed in apickup truck equipped with a fuel injected NGV conversion system. Theregulator replaced the single stage mechanical regulator and was testedon a chassis dynamometer. Instrumentation was installed to measurepressure and flow rate.

[0123] Experimental Procedure

[0124] Two tests using air as a test gas were conducted on a singlestage mechanical regulator and a regulator according to the presentinvention as described in the following.

[0125] 1) A flow test was conducted to determine the change in theoutlet pressure as a function of a change in flow rate.

[0126] 2) An inlet pressure test was conducted to determine the changein outlet pressure as a function of a change in inlet (supply) pressure.

[0127] The intent of the initial test is to determine the error inpressure that can occur at different flow rates as engine operationchanges from idle to wide open throttle. The second test evaluates thechange in regulator pressure as the tank pressure decreases from full toempty.

[0128] Procedure for Flow Test

[0129] 1) The supply pressure was set at 1000 psig.

[0130] 2) The regulator pressure was set at 100 psig at a 1 g/s flowrate.

[0131] 3) A needle valve controlling the outlet flow was turned off andthe flow rate reduced to zero.

[0132] 4) The flow rate was increased in a ramp by slowly opening theneedle valve, increasing the flow rate from zero to 20 g/s over 50seconds, then the needle valve was closed slowly decreasing the flowrate back to zero over 50 seconds.

[0133] 5) The supply pressure was kept constant during the tests byadjusting a high-pressure regulator on the air supply cylinders.

[0134] 6) Data for supply pressure, outlet pressure, and flow rate wererecorded on a Campbell Scientific data logger.

[0135] 7) Graphs were produced that plotted outlet pressure and flowrate versus time and outlet pressure versus flow rate.

[0136] 8) Dynamic droop, hysteresis, and cracking droop were scaled fromthe plots.

[0137] Procedure for Inlet Pressure Test

[0138] 1) The regulator pressure was set at 100 psig at 1 g/s flow rate.

[0139] 2) The regulator supply pressure was set to zero.

[0140] 3) The tank pressure was increased in a ramp from zero to 2 100psig over a 70 second period, then it was decreased from 2 100 psig tozero over 70 seconds.

[0141] 4) Data for supply pressure, outlet pressure, and flow rate wererecorded on a Campbell Scientific data logger.

[0142] 5) The data was displayed in a spread sheet and a graph wasproduced that plotted outlet pressure versus inlet pressure.

[0143] 6) The change in outlet pressure due to the change in inletpressure was scaled from the plots.

[0144] Analysis of Results

[0145] Dynamic Droop

[0146]FIGS. 5 and 6 compare the dynamic droop as a function of time andflow rate for the single stage mechanical regulator and the electronicregulator. The results for air flow rates of 20 and 10 g/s, which werescaled from FIGS. 7 and 8, are summarized in Table 2. The calculation isbased on the average change in pressure, neglecting the hysteresis. Forexample, the mechanical regulator has a droop of 22 psig (98 psig−76psig) for increasing flow and 20 psig (103 psig−83 psig) for decreasingflow. Hence, the average droop is 21 psig. Values are also shown for aflow rate of 10 g/s. TABLE 2 Dynamic Droop Comparison RegulatorMechanical (psig) Electronic (psig) at 20 g/s 21 2 at 10 g/s 6 1

[0147] Note that these results are for a test setup with a prototypeelectronic regulator. It is believed that the droop in the electronicregulator could be reduced even further in an optimized design withshorter line lengths and a higher control pressure. As well, the noisyoutlet pressure shown in FIGS. 6 and 8 appears to be a characteristic ofthe single valve design (FIG. 1) that may not exist with dual valves(FIG. 2). In actual use the noise may be over shadowed by the noise fromfuel injectors.

[0148] Hysteresis

[0149]FIGS. 7 and 8 were used to calculate the hysteresis for themechanical and electronic regulators. It was calculated by scaling thedifference in the outlet pressure curves at 5 g/s intervals for flowrate increasing and decreasing. The average of five points from 0 to 20g/s was taken as the droop for the test. For example, the hysteresis forthe mechanical regulator at 0, 5, 10, 15, and 20 g/s are respectively 5,6, 7, 7, and 6 psig. And the average is 6.2 psig. The results aresummarized in Table 3. Regarding the electronic regulator, the outletpressure is noisy as shown in FIG. 8, but the hysteresis is essentiallyzero. TABLE 3 Hysteresis Comparison Regulator Single-Stage ElectronicHysteresis (psig) 6.2 0

[0150] Cracking Droop

[0151] Cracking droop was scaled from FIGS. 7 and 8. For the mechanicalregulator the static pressure is 104 psig as shown in FIG. 7; however,as soon as the flow starts the pressure reduces to 98 psig; hence, thecracking droop is 6 psig. The results are summarized in Table 4. Notethat the cracking droop for the electronic regulator is somewhatundefined since it is over shadowed by cyclic variations of the outletpressure. TABLE 4 Cracking Droop Comparison Regulator Single-StageElectronic Cracking Droop (psig) 4 1

[0152] Cyclic Fluctuations

[0153] Cyclic variations were estimated from FIGS. 7 and 8. Thesefigures provide the best representation of the pressure variation as afunction of flow rate. The results shown in Table 5 represent the noisein the outlet pressure as the flow rate is increased then decreased. Arange is presented because it is difficult to establish a representativevalue. Cyclic variations for the mechanical regulators may be due to thespring, mass, damper effect in the fluid control system. The controlchamber or “dome” of the electronic regulator is either being fed orbled at all times which results in the variability in the controlpressure, and consequently the variability in the outlet pressure. Theamplitude of this cyclic behaviour may be reduced through optimizingcontroller gains and filtering the noise in the outlet hose. TABLE 5Limit-Cycle Fluctuations (psig) Regulator Single-Stage Electronic LimitCycle ±0.5 to ±1 ±1.5 to ±5

[0154] Note that statistical analysis of the pressure noise is notwarranted because it is overwhelmed by the pressure fluctuations createdby the fuel injectors.

[0155] Inlet Pressure Effect

[0156] The change in outlet pressure due to changes in inlet pressurewas estimated from FIGS. 9 and 10 for the single-stage and electronicregulators respectively. Only the pressure decreasing part of each testwas used to determine the inlet pressure effect. It was estimated on aper 1000 psig basis since the tests were done over the range of 0 to2400 psig. Hence, an extrapolation is required for higher pressures(3600psig). FIG. 9 shows a very small inlet pressure effect for thesingle-stage regulator as the pressure is increased; however, as theinlet pressure is decreased from 2400 psig to 150 psig the inletpressure drops from 102.5 psig to 97.5 psig. The result is an inletpressure effect of 2.6 psig/1000 psig ((102.5−97.5)/(2100−150)×1000) asshown in Table 6. TABLE 6 Inlet Pressure Effect Comparison (psig/1000psig inlet) Regulator Single-Stage Electronic Variance 2.6 0.9

[0157] Maximum Regulation Error

[0158] The maximum pressure error that might be realized in a vehicle isa function of the dynamic droop at 20 g/s, the hysteresis, and the tankpressure effect. Cyclic variations are ignored because they will be overshadowed by the pressure fluctuations caused by the fuel injectors (asmentioned later). Cracking droop for the mechanical and electronicregulators is ignored as well since this error only occurs only when avehicle is started. As well, the transient error exhibited by theelectronic regulator on a fuel flow decrease is ignored since it can becorrected. Equations I and 2 were used to calculate the maximum errorand the percent maximum error; the results are summarized in Table 7.TABLE 7 Total Regulator Error Regulator Single-Stage Electronic MaximumError (psig) 32 5 Percent Maximum Error 28 4

[0159] Vehicle Testing

[0160] The prototype electronic regulator was installed in a 1992 GMpickup truck with a 5.0-L engine, replacing the regulator in a naturalgas fuel-injection conversion system. The vehicle was installed on achassis dynamometer and driven through two test cycles: a maximum powertest at wide-open throttle (WOT), and the Hot 505 part of the FederalTest Procedure (FTP-75) used to evaluate tailpipe emissions. The vehicleworked very well with the electronic regulator. FIGS. 11 and 12 comparethe results from the electronic regulator to results from a single-stagemechanical regulator. Note that the cyclic fluctuations for theelectronic regulator and mechanical regulator are about the same inmagnitude and frequency. It appears that the fluctuations caused by thefuel injectors over shadow the regulator fluctuations.

[0161] For the WOT test, the natural gas flow rate is shown increasingfrom 0.2 to 7 g/s. The outlet pressures from the mechanical regulatorand electronic regulator are plotted on the same scale. The mechanicalregulator has a droop ranging from about 3 to 7 psig while theelectronic regulator has a droop of less than 2 psig.

[0162] The flow rate in the Hot 505 test, which ranges from about 0. 1to 3 g/s, represents a combination of speed and load as the vehicle isaccelerated and decelerated on the dynamometer. The mechanical regulatorshows a droop of about 3 psig during transients while the electronicregulator shows essentially zero droop.

[0163] The present invention thus provides an electronic regulator forNGV applications that is more accurate than mechanical regulators. Inpreferred embodiments it has the capability to set the outlet pressureon-line. The maximum error in the prototype electronic regulator is 4%,compared to a two-stage mechanical regulator at 18%, and a single-stagemechanical regulator at 28%. This should have a significant effect onthe performance and emissions of natural gas vehicles.

[0164] Chassis dynamometer tests in a GM pickup truck showed that theelectronic regulator worked well, improving accuracy over the mechanicalregulator. The tests showed that droop can be reduced to zero in the Hot505 driving cycle.

[0165] Bench tests demonstrate that the outlet pressure can be varieddynamically in response to given input parameters or based on elapsedtime. An example is shown in FIG. 13 in which the output pressurefollows a pre-programmed ramp output.

1. A gas pressure regulator for regulating the pressure of a gas flowingfrom a source of the gas under pressure to a device for using the gas,the regulator comprising: a regulator housing having a gas inlet forreceiving the gas and a gas outlet for the delivery of the gas from thehousing; a pressure reducing valve in the housing for controlling theflow of gas from the inlet to the outlet; a pressure reducing valvecontroller comprising: a control chamber; a feed valve having an inletfor receiving gas from said source of gas under pressure and a controlpressure outlet coupled to the control chamber, the feed valve having anopen state in which the valve is fully open and a closed state in whichthe valve is fully closed; a bleed valve having an inlet coupled to thecontrol chamber and an outlet coupled to the gas outlet of the regulatorhousing, the bleed valve having open state in which the valve is fullyopen and a closed state in which the valve is fully closed; a high speedsolenoid valve actuator for operating the feed and bleed valves; apressure responsive member in the control chamber and coupled to thepressure reducing valve for movement therewith, the pressure responsivemember being movable in response to variations in a control pressure inthe control chamber; a pressure monitor for monitoring an actual gaspressure at the gas outlet of the regulator housing; a controllercoupled to the pressure monitor and to the solenoid valve actuator forcontrolling operation of the feed and bleed valves between theirrespective closed and open states to produce a desired gas pressure atthe gas outlet of the regulator housing.
 2. A gas pressure regulatoraccording to claim 1 wherein the desired gas pressure at the gas outletis a set point pressure and the controller comprises a mechanism forcontrollably varying the set point pressure.
 3. A gas pressure regulatoraccording to claim 1 wherein the controller includes a signal generatingmechanism for delivering a pulsed electrical signal for operating thefeed and bleed valves and a signal varying mechanism for controllablyvarying the pulse width of the electrical signal.
 4. A gas pressureregulator according to claim 1 wherein the high speed solenoid valveactuator includes a pressure reducing valve closing mechanism forclosing the pressure reducing valve in response to deactivation of thehigh speed solenoid valve actuator.
 5. A gas pressure regulatoraccording to claim 1 wherein the feed and bleed valves are coupled formovement together between a bleed position in which the bleed valve isin the open state and the feed valve is in the closed state and a feedposition in which the feed valve is in the open state and the bleedvalve is in the closed state.
 6. A gas pressure regulator according toclaim 5 wherein the high speed solenoid valve actuator comprises asingle solenoid coupled to the feed and bleed valves, the feed and bleedvalves being positioned in the bleed position upon deactivation of thesingle solenoid.
 7. A gas pressure regulator according to claim 1wherein the feed and bleed valves are coupled to communicate with thecontrol chamber on a first side of the pressure responsive member.
 8. Agas pressure regulator according to claim 7 wherein there is provided aport coupling the control chamber on a second side of the pressureresponsive member to the gas outlet of the regulator housing such thatback pressure on the second side of the pressure responsive member issubstantially equal to the actual gas pressure at the gas outlet.
 9. Agas pressure regulator according to claim 7 wherein there is provided abiasing mechanism acting on the pressure responsive member in adirection corresponding to closing the pressure reducing valve.
 10. Agas pressure regulator according to claim 1 wherein there is provided ashut-off valve coupled to the gas inlet of the regulator housing, theshut-off valve being arranged to be closed in response to a shut-offcondition sensed by the pressure monitor.
 11. A gas pressure regulatoraccording to claim 10 wherein the shut-off valve includes a solenoidoperating mechanism for displacing the valve between respective open andclosed positions, the solenoid operating mechanism being oriented in theclosed position when deactivated.
 12. In combination: a supply ofpressurised gas; a gas using device for using the pressurised gas; and agas pressure regulator coupled to the gas using device and the supply ofpressurised gas for controlling the pressure of gas delivered from thesupply to the gas using device, said pressure regulator comprising: aregulator housing having a gas inlet for receiving the gas and a gasoutlet for the delivery of the gas from the housing; a pressure reducingvalve in the housing for controlling the flow of gas from the inlet tothe outlet; a pressure reducing valve controller comprising: a controlchamber; a feed valve having an inlet for receiving gas from said sourceof gas under pressure and a control pressure outlet coupled to thecontrol chamber, the feed valve having an open state in which the valveis fully open and a closed state in which the valve is fully closed; ableed valve having an inlet coupled to the control chamber and an outletcoupled to the gas outlet of the regulator housing, the bleed valvehaving open state in which the valve is fully open and a closed state inwhich the valve is fully closed; a high speed solenoid valve actuatorfor operating the feed and bleed valves; a pressure responsive member inthe control chamber and coupled to the pressure reducing valve formovement therewith, the pressure responsive member being movable inresponse to variations in a control pressure in the control chamber; apressure monitor for monitoring an actual gas pressure at the gas outletof the regulator housing; a controller coupled to the pressure monitorand to the solenoid valve actuator for controlling operation of the feedand bleed valves between their respective closed and open states toproduce a desired gas pressure at the gas outlet of the regulatorhousing.
 13. A combination according to claim 12 wherein the supply ofpressurised gas is mounted remotely from the gas using device, coupledby a gas line and wherein the gas pressure regulator is mounted adjacentthe supply of pressurised gas.
 14. A combination according to claim 13wherein the pressure monitor is coupled to the gas line adjacent the gasusing device.
 15. A combination according to claim 12 wherein the gasusing device comprises an internal combustion engine.
 16. A combinationaccording to claim 12 wherein the gas using device comprises a fuel cellpowered engine.
 17. A method of regulating pressure of a gas flowingfrom a source under pressure to a device for using the gas, the methodcomprising: providing a regulator housing having a gas inlet, a gasoutlet and a pressure reducing valve for controlling the flow of gasfrom the inlet to the outlet; connecting the gas inlet in communicationwith the source under pressure; connecting the gas outlet incommunication the device for using the gas; providing a pressurereducing valve controller having a control chamber, a feed valve and ableed valve, each of the feed and bleed valves having an open state inwhich the valve is fully open and a closed state in which the valve isfully closed; connecting the feed valve to the source under pressure atan inlet of the feed valve and to the control chamber at an outlet ofthe feed valve; connecting the bleed valve to the control chamber at aninlet of the bleed valve and to the gas outlet of the regulator housingat an outlet of the bleed valve; providing a pressure responsive memberin the control chamber; coupling the pressure responsive member to thepressure reducing valve for movement therewith in response to variationsin control pressure in the control chamber; monitoring an actual gaspressure at the gas outlet of the regulator housing; and controlling, inresponse to the actual gas pressure monitored, operation of the feed andbleed valves between their respective closed and open states to producea desired gas pressure at the gas outlet of the regulator housing. 18.The method according to claim 17 wherein controlling operation of thebleed valve includes venting the control chamber to the gas outlet ofthe regulator housing.
 19. The method according to claim 18 includingmaintaining the control pressure in the control chamber substantiallygreater than the actual gas pressure at the gas outlet of the regulatorhousing.
 20. The method according to claim 17 including operating thefeed and bleed valves together between a bleed position in which thebleed valve is in the open state and the feed valve is in the closedstate and a feed position in which the feed valve is in the open stateand the bleed valve is in the closed state.